Herbicidal benzothiadiazoles and oxygen and selenium analogues



United States Patent 3,478,044 HERBICIDAL BENZOTHIADIAZOLES AND OXYGEN AND SELENIUM ANALOGUES Robert S. Slott, Berkeley, Edward R. Bell, Walnut Creek, and Kurt H. G. Pilgram, Modesto, Calif., assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Dec. 9, 1966, Ser. No. 600,371 Int. Cl. C07d 99/00 U.S. Cl. 260-298 6 Claims ABSTRACT OF THE DISCLOSURE Novel herbicidal 2,1,3 benzothiadiazoles substituted by at least one of cyano and thiocarbamoyl, and their oxygen and selenium analogues.

This invention relates to novel compounds useful in destroying and/or preventing growth of unwanted'plants.

These novel herbicidal compounds are represented by the generic formula:

i \3 (Y). N

wherein R is oxygen, sulfur or selenium, X is cyano (CN) or thiocarbamoyl (C(S)NH n is a Whole number from zero to three, and Y is middle halogen (i.e., bromine or chlorine), nitro (-NOg), lower alkyl, amino (NH cyano or thiocarbamoyl.

In these compounds, any alkyl substituent preferably contains no more than two carbon atoms.

In these compounds, highest herbicidal activity occurs when the substituent, X, is bonded to one of the carbon atoms in the 4- and 7-positions on the ring. Within this subgenus, two classes appear to exhibit the highest activity:

(a) The class wherein n is 1 and Y is cyano or thiocarbamoyl;

(b) The class wherein n is 2 and one Y is methyl, the

other Y being cyano or thiocarbamoyl.

Typical species, illustrating the genus of herbicidal compounds of this invention, are set out in the examples presented hereinafter showing preparation and herbicidal screening of those species.

The compounds of the invention wherein X is cyano are readily prepared by mixing the corresponding bromo benzothiadiazole, benzofurazan or benzoselenadiazole with the theoretical amount of cuprous cyanide in a highly polar aprotic solvent, such as dimethylformamide, pyriidine or dimethylsulfoxide, and heating the resulting mixture. The compounds wherein n is 1 or more, and one or more of Y is cyano, can be prepared in alike manner from the corresponding substituted benzothiadiazole, benzofurazan or benzoselenadiazole precursors. The manner in which the conversion is carried out is illustrated in the examples set out hereinafter.

The compounds of the invention wherein X is thiocarbamoyl are readily prepared by reacting the appropriate compound of the invention wherein X is cyano with hydrogen sulfide (to completion of reaction) in the presence of ammonia or a base such as diethanolamine. Where ammonia is employed, a lower alkanol such as methanol or ethanol is a suitable solvent; wherein diethanolamine or similar base is employed, dimethylformamide is a suitable solvent. Where n is one or more, and one or more of Y is thiocarbamoyl, the compound can be prepared in a like Patented Nov. 11, 1969 Example I.Preparation of 2,1,3-benzothiadiazole-4,7-

dicarbonitrile 10 parts of 4,7-dibromo-2,1,3-benzothiadiazole was mixed with 6.1 parts of cuprous cyanide and the mixture stirred into parts by volume of dimethylformamide. The mixture was stirred for 19 hours at reflux temperature ISO- C.). It then was cooled and filtered to remove solid material that had formed. The filtrate was mixed with 15 0 parts by volume of water. A precipitate formed and was removed by filtration. The precipitated material was dissolved in concentrated ammonium hydroxide and the solution extracted with benzene. The product was ob tained as the solid matter remaining following the extraction. The product sublimes. It was identified by elemental analysis as 2,1,3-benzothiadiazole-4,7-dicarbonitrile, which melts at 187-189 C. (sealed tube), when recrystallized from methyl ethyl ketone.

Analysis (percent by weight). Calculated: C, 51.5; H, 1.1; N, 30.1. Found: C, 51.4; H, 1.1; N, 29.0.

The identity of the product was confirmed by infra-red and mass spectrum analysis.

Example IL-Preparation of 4,7-benzofurazandicarbonitrile 45 parts of 4,7-dibromobenzofurazan was dissolved in 400 parts by volume of dimethylformamide. 30 parts of cuprous cyanide was added and with constant stirring the mixture wash eated to 150-155 C. and held there, total time: 1.5 hours. The solvent then was stripped off under reduced pressure, and the residue was extracted with xylene. The xylene extract was evaporated to leave 13.5 parts of crude product, which on crystallization from ethanol gave 12 parts of 4,7-benzofurazandicarbonitrile as brown crystals melting at -188 C. The identity of the product was established by elemental analysis:

Calculated: N, 38.8; Br, 0. Found: N, 38.9; Br, less than 0.2.

The identity of the product was confirmed by its infrared spectrum and by gas-liquid chromatography procedure.

Example III.-Preparati0n of 5-chloro-4-carbonitrile- 2,1,3-benzothiadiazole 20 parts of 4-bromo-5-chloro-2,1,3-benzothiadiazole, 7.2 parts of cuprous cyanide and 200 parts by volume of dimethylformamide were placed in a reactor and the mixture stirred and heated at reflux (approximately 153 C.) for approximately 3.5 hours. The solvent then Was stripped off under reduced pressure. The residue was taken up in 100' parts by volume of concentrated hydrochloric acid and 100 parts by volume of benzene. 25 parts by volume of 30% hydrogen peroxide in water was added dropwise to the stirred mixture over a period of 45 minutes, the mixtures being maintained at 40 C. The mixture was stirred for an additional 30 minutes after the hydrogen peroxide had all been added. The mixture then was filtered and the filtrate phase-separated. The filter cake and the aqueous phase were each extracted with benzene, the benzene solutions combined, dried, filtered and benzene removed to yield 17 parts of crude product. Recrystallization from methanol yielded 8 parts of 5- chloro 4 carbonitrile 2,1,3 benzothiadiazole, color- 3 less crystals melting at 172-175 C. The identity of the product was established by elemental analysis, and infrared spectrum analysis.

Example IV.-Preparation of 4,7-di(thiocarbamoyl)- plants in soil treated with the test compounds at the rate of 10 pounds per acre. Seeds of watergrass and cress were planted in treated soil and the planted soil held under controlled conditions of temperature, moisture and light for 13 to 14 days. The amount of germination then was 213 benZOth1ad1aZo1e 5 noted, and the efiectiveness of the test compound rated 20 Parts of 2,L3-bBHZOthiadiaZOIe-4J dicarbonitrile on the basis of a 0 to 9 scale, 0 rating indicating no eifect, and 1500 Parts y Volume of methanol were introduced 9 indicating death of seedlings or no germination. The reinto a reactor. Anhydrous ammonia was bubbled into the sults are Summarized i Table The pospemergence Stirred miXtllre f 0 Ininllt6$- Then hydrogen Sulfide tivity of compounds of the invention was evaluated by and ammonia were bubbled into the stirred mixture for Spraying 10-d 1d i d l t d 7-d ld b an additional 3 hours. The mixture spontaneously heated grass p1ants with a liquid fo l ti f the test to 50 C. The mixture then was cooled in an ice bath and pound t th t f 10 pounds f t t compound r Was filtfired- 17 Parts of a maroon Colored Solid Product acre. The sprayed plants then were held under controlled Was Obtained, melting at 9 6 With decompositionconditions of temperature, moisture and light for 10-11 It was identified by elemental analysis: days. The effect of the test chemical then was evaluated Calculated? Found! visually, the results being rated on a 0 to 9 scale, 0 rating N, 22.2; S, 36.1;C, 38.8;H, 2.1. indicating no effect, 9 rating indicating complete kill of The identity was confirmed by infra-red Spectrum analthe plants. The results are also summarized in Table I. ysrs.

4,7 di(thiocarbamoyl) 2,1,3 benzothiadiazole also TABLE I was prepared in a similar manner employing diethanol- Pre'emergence Poswmergence amine (one mole per mole of dicarbonitrile reactant) iIl- Water-grass Cress Crabgrass Pigweed stead of ammonia, and dimethylformamide as solvent. Compound: The product was a brick-red solid melting at 26l-262 C. A 9 9 9 9 with decomposition. It, too, was identified by elemental g g g g and infrared spectrum analysis. 3 g 3 3 Example V.Preparation of 5-methyl-4,7-di(thiocar- 9 9 9 9 bamoyl)-2,1,3-benzothiadiazole 3O 3 3 3 3 In a manner similar to that described in Example I, 5- g g g g methyl-4,7 dicarbonitrile 2,1,3 benzothiadiazole was 8 g g 3 prepared from 5-methyl-4,7-dibromo-2,1,3-benzothiadia- 9 9 6 9 zole. g g g g 2 parts of 5 methyl 4,7 dicarbonitrile 2,1,3-benzothiadiazole and 150 parts by volume of ethanol were placed in a reactor, and ammonia and hydrogen sulfide other P? of the lnfentlon Whlch have been were bubbled into the stirred mixture for minutes. The found to actlve 111 these tests Include: mixture then Was cooled in an ice bath and filtered- 2 5,7-dichloro-2,1,3-benzothiadiazole-4-carbonitrile Parts of fed-brown colored Solid, melting at 235-2380 -i 4 4-nitro-2,1,3-benzothiadiazole-5,7-dicarbonitrile was obtained. The product was identified as 5-methyl-4,7- 4 7 di(thi b l)b f Q Y benzothiadialole y elemental 5-amino-2,1,3-benzothiadiazole-4,7-dicarbonitrile y 4,7-di(thiocarbamoyl)-5,6-dimethyl 2,1,3 benzothiadia- Calculated: N, 23.9; S, 27.3. Found: N, 23.5; S, 26.9. 1 h identity was confirmed y infra-red Spectrum anal- 45 5,6-dimethyl-2,l,3 benzothiadiaz0le-4,7-dicarbonitrile SIS. y By similar procedures other species of the compounds Example VII of this inventi n W r prep r The preand post-emergence herbicide activity of com- The following compounds of the inventi n were teste pounds of the invention was further evaluated by spraying to ascertain their eifectiveness as herbicides, the com- 5 seeded oil, and growing plants respectively, with a 1:1 pounds being identified in terms of the following formula: etone-water formulation of the test compound, then w N holding the sprayed soil or plants under controlled con- X ditions for l0-11 days, then ascertaining the effect of the R test compound in each case. The seeded soil and plants Y were held in small pots, placed side-by-side. The spraying was so conducted that the dosage varied logarithmically Z over a series of the pots. The results in each case were re- R W X Y 2 Compound:

A Sulfur Cyano H H Cyano.

rln dn H C do Thiocarbamoyl g.

d H do. Thioearbamoyl H t T do Cyann Cyano Thiocarbamoyl H.

Bromlne.

.do H Oyano. Seleniurn Cyano H Example VI The pre-emergence herbicidal activity of compounds of ported in terms of the LD dosage (dosage in pounds per acre to give control 95% control of the test plant).

the invention was evaluated by planting seeds of test The plants used, the test compounds used and the LD dosages for each test plant/test compound combination are summarized in Table II and III.

TABLE II Per-emergence application Rye- Cheat- Grabgrass grass grass Dock Pigweed Mustard Compound:

TABLE III Post-emergence application Wild Water- Crab- Fiddle- Field Oats grass grass neck cress Compound:

It is evident from the results of all of these tests that compounds of the invention are generically powerful broad-spectrum herbicides, whether applied pre-emergence or post-emergence.

The compounds of this invention are in general solids of very low volatility that are rather insoluble in water and the common organic solvents used in applying herbicides. Consequently, it Will be found that compounds of the invention are most readily and effectively applied as herbicides formulated as wettable powders, or as granules for application to soil. Thus, the compound can be adsorbed or absorbed in or on a sorptive carrier, such as finely divided clay, talc, gypsum, lime, wood flour, fullers earth, kieselguhr, or the like. The solid composition, or dust, may contain from as little as 1% 'by weight of active material to 75% by weight of active material, or even more. It may be prepared as a dust, or as granuels designed to be broadcast or to be worked into the soil. Wettable powders can be prepared suitable for suspension in water with or without the aid of conventional dispersing or deflocculating agents and with or without such adjuvants as oils, stickers, wetting agents, etc.

For field application, the rate of application of the active agent may be varied from about 0.1 to 30 or more pounds per acre. It will be appreciated that the rate of application is subject to variation according to the particular active agent used, the particular species of plants involved, and the local conditions, for example, temperature, humidity, moisture content of the soil, nature of the soil, and the like. Effective resolution of these factors is well within the skill of those well versed in the herbicide art.

The herbicidal compositions may contain one or more of the herbicidal compounds set out hereinbefore as the sole active agent, or they may contain in addition thereto other biologically active substances. Thus, insecticides, e.g., DDT, endrin, dieldrin, aldrin, chlordane, demeton, methoxychlor, DDVP, naled, alpha-methylbenzyl 3-hydroxycrotonate dimethyl phosphate and 3-hydroxy-N,N-

dimethyl crotonamide dimethyl phosphate, rotenone and MW pyrethrum, and fungicides, such as copper compounds,

such as naphthalene acetic acid, 2,4-dichlorophenoxyacetic acid and the like, and/or herbicides of difierent properties.

Because the compounds of the invention are not very volatile, and are rather insoluble in water, they tend to remain in that part of the soil into which they are introduced, even heavy leaching with water tending to move them only slightly through soil.

Consequently, by appropriate selection of the part of the soil into which they are introduced, relative to the seeds of wanted plants and those of unwanted plants, and taking into account the effect of water, these herbicides can be used to prevent all plant growth, even at relatively low dosages in some cases, or their selectivity can be improved to prevent growth of unwanted plants without harm to wanted plants. For example, as is well known, only those weed seeds which are present within about one-quarter inch of the surface of the soil will germinate, whereas the seeds of cereal, and other, crops, for example, ordinarily are sown about one-half to threequarters of an inch below the surface of the soil, an germinate well under those conditions. By introducing the herbicide only into the top one-quarter inch of the soil, and avoiding excessive watering, germination of the weed seeds can be prevented, while germination of the crop seeds will not be elfected. Thus, even those herbicides of this invention that are not very selective in their action can be used to selectively remove the weeds from cereal grains or other crops. Of course, if complete kill of all plants in a given portion of soil is desired, it is necessary only to introduce one or more of the herbicides throughout that portion of soil.

We claim as our invention:

1. A compound of the formula:

(Y). N wherein R is oxygen, sulfur or selenium, X is cyano thiocarbamoyl, n is a whole number from zero to three and Y is middle halogen, nitro, lower alkyl, amino, cyano or thiocarbamoyl.

2. A compound according to claim 1 wherein X is bonded to a carbon atom in either the 4- or 7-position of the ring, n is 1 and Y is cyano or thiocarbamoyl.

3. A compound according to claim 1 wherein X is bonded to a carbon atom in either the 4- or 7-position of the ring, n is 2, one Y is methyl, the other Y being cyano or thiocarbamoyl.

4. A compound according to claim 2 in which X and Y both are cyano.

5. A compound according to claim 4 in which X is bonded to the carbon atom at the 4-position of the ring, and Y is bonded to the carbon atom at the 7-position of the ring.

6. A compound according to claim 2 in which X and Y both are thiocarbamoyl.

References Cited UNITED STATES PATENTS 3,279,909 10/1966 Daams et al. 260304 3,337,572 8/1967 Kilsheimer et al. 260307 ALEX MAZEL, Primary Examiner R. I. GALLAGHER, Assistant Examiner U.S. Cl. X.R. 

